<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>
<body>

  <div id="app">
    姓：<input type="text" v-model="firstName"><br>
    名：<input type="text" v-model="lastName"><br>
    <p>姓名：{{ fullName }}</p>
    <button @click="changeFullName">修改姓名</button>
  </div>
  <script src="./vue.js"></script>
  <script>
    const app = new Vue({
      el: '#app',
      data: {
 firstName:'张',
 lastName:'三',
      },
      computed: {
     fullName:{
      get(){
        return this.firstName+this.lastName
      },
      set(newValue){
        this.firstName=newValue.slice(0,1);
        this.lastName=newValue.slice(1);
      }
     }
      },
      methods: {
    changeFullName(){
      this.fullName='王二麻子';
    }
      }
    })
  </script>
</body>
</html>